Group III-V nitride semiconductors have been variously applied to an optical device such as blue and green light emitting diodes (LED), a high speed switching device, such as a MOSFET (Metal Semiconductor Field Effect Transistor) and an HEMT (Hetero junction Field Effect Transistors), and a light source of a lighting device or a display device. In particular, light emitting devices using group III nitride semiconductors have a direct transition-type bandgap corresponding to the range from visible rays to ultraviolet rays, and can perform high-efficiency light emission.
The nitride semiconductor is mainly used for the LED (Light Emitting Diode) or an LD (laser diode), and studies have been continuously conducted to improve the fabrication process or light efficiency of the nitride semiconductor.